This is a competing continuation of a multi-method longitudinal study of developmental trajectories of reactivity and regulation among cocaine and non-cocaine exposed infants. The original application focused on reactivity and regulation of infants and toddlers at 1, 7, 13, and 24 months of age using both behavioral and autonomic measures. In a competitive supplement, we initiated a 36 and 48 month follow-up to examine the development of self-regulation and autonomic regulation under conditions of mild stress. We also initiated brief home visits at 18, 30, 42, and 54 months of age in order to maintain contact and collect data on continued maternal substance use and reports of children's behavior. The specific aims of this application are as follows: 1) To complete assessments of ongoing maternal substance use, mediator variables, and self-regulation among cocaine-exposed and non-cocaine-exposed children at 36 and 48 months; 2) To initiate and complete assessments of this sample upon entry into kindergarten on key predictor (maternal cocaine and other substance use), mediating (parenting, infant risk characteristics, caregiving environment), and outcome variables (self-regulation and social competence); 3) To examine if the relationship between maternal substance use and the development of self-regulation and social competence is mediated by maternal parenting behavior, the caregiving environment, or infant risk characteristics; 4) To examine reasons for heterogeneity in regulatory outcomes and social competence among cocaine-exposed and non- cocaine-exposed children. The final sample consists of 220 mother-infant dyads (120 in the cocaine group and 100 in the control group) recruited at birth. Data analyses focuses on examining developmental trajectories of self-regulation as a function of prenatal exposure to cocaine and other substances, fetal and neonatal infant risk characteristics, parenting, and the quality of the caregiving environment. It is hypothesized that developmental trajectories of self-regulation from the toddler/preschool period will predict self-regulation and social competence in kindergarten. This study utilizes a developmental psychopathology perspective to examine transactional influences on development and multiple pathways to risk and resilience among substance exposed infants.